Rainfall is intermittent and variable. Sometimes rainfall variations are regular with the seasons. In other instances, rainfall fluctuates over longer periods of time. The variability of rainfall has forced man to develop systems to collect water when available to provide water when rain is scarce.
In a more contemporary perspective, water supplies, particularly in the Southwestern United States have come under particular pressure arising from increasing populations and what appears to be increasing rainfall variability.
In response to rainfall variability, the collection of rain has been undertaken for centuries. Cisterns were used in the classic era to hold rainwater collected from roofs and more recently, rain collection receptacles such as rain barrels have been located in suburban neighborhoods. These are found with increasing frequency throughout the Southwestern United States to supplement local supplies at reasonable cost.
The water collected from rainfall, either through especially constructed collection systems or from structures such as roofs, for example, will typically include unwanted material washed into the collection systems and receptacles. Without some sort of filtration or selection system, vegetative matter such as leaves and twigs along with animal waste such as bird droppings, will frequently wash into the storage receptacles of water collection systems.
Consequently, a variety of filtration systems have been developed to inhibit the collection of unwanted material and waste in rain collection systems. Such systems have used a variety of techniques such as direct filtration through mesh or fiber screens while other systems have used cyclonic or circulatory action to assist the passage of higher quality water through filters while leaving the more debris laden water for differential collection.
In each case, however, the filtering system has added complexity and unsightly apparatus to filtration systems. This is of particular concern in residential installations where rain barrels are increasing in use. Most available filtration systems add visible plumbing and unsightly complexity to what should preferably be utilitarian and unobtrusive installations whether devised to enhance the water supply for residential water users while lowering the load on the neighborhood or city supply facilities or providing water supplies in locations far removed from established supplies.
What is needed therefore is a filtration system devised to remove substantial amounts of unwanted debris and residue from rain water before collection for later use while minimizing the visibility of the filtration apparatus.